[Bug analyzer/104224] New: Testcases for analyzer "uninit" from fedora-devel

[Bug analyzer/104224] New: Testcases for analyzer "uninit" from fedora-devel

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

            Bug ID: 104224
           Summary: Testcases for analyzer "uninit" from fedora-devel
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: analyzer
          Assignee: dmalcolm at gcc dot gnu.org
          Reporter: dmalcolm at gcc dot gnu.org
  Target Milestone: ---

Steve Grubb posted some test cases for detecting uninit bvehavior to Fedora's
development list here:
 
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.org/message/S75EUIQ5Y3MXNXVPFFX4XHE7CW3SKULU/
("Re: Uninitialized variables and F37")

I'm filing this bug as a reminder to add the cases to the regression test
suite, and to fix any false positives/negatives.

[Bug analyzer/104224] Testcases for analyzer "uninit" from fedora-devel

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

--- Comment #1 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
gcc trunk with -fanalyzer: https://godbolt.org/z/T17TbqYdx

[Bug analyzer/104224] Testcases for analyzer "uninit" from fedora-devel

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

--- Comment #2 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:9ff3e2368d86c1bf7d1e8876a14e58c0d6617ffe

commit r12-6876-g9ff3e2368d86c1bf7d1e8876a14e58c0d6617ffe
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Tue Jan 25 14:10:46 2022 -0500

    analyzer: fix missing uninit warning on args to stdio builtins [PR104224]

    We were failing to check for uninitialized arguments to stdio builtins,
    such as when passing local "go" to the call to "printf" in "main" in
    the testcase.

    gcc/analyzer/ChangeLog:
            PR analyzer/104224
            * region-model.cc (region_model::check_call_args): New.
            (region_model::on_call_pre): Call it when ignoring stdio builtins.
            * region-model.h (region_model::check_call_args): New decl

    gcc/testsuite/ChangeLog:
            PR analyzer/104224
            * gcc.dg/analyzer/pr104224.c: New test.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

[Bug analyzer/104224] Testcases for analyzer "uninit" from fedora-devel

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:00e7d024afb80e95fb36d74b1c059468d883a850

commit r12-6906-g00e7d024afb80e95fb36d74b1c059468d883a850
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Wed Jan 26 16:24:08 2022 -0500

    analyzer: show region creation events for uninit warnings

    When reviewing the output of -fanalyzer on PR analyzer/104224 I noticed
    that despite very verbose paths, the diagnostic paths for
      -Wanalyzer-use-of-uninitialized-value
    don't show where the uninitialized memory is allocated.

    This patch adapts and simplifies material from
      "[PATCH 3/6] analyzer: implement infoleak detection"
        https://gcc.gnu.org/pipermail/gcc-patches/2021-November/584377.html
    in order to add region creation events for the pertinent region (whether
    on the stack or heap).

    For example, this patch extends:

    malloc-1.c: In function 'test_40':
    malloc-1.c:461:5: warning: use of uninitialized value '*p' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
      461 |   i = *p;
          |   ~~^~~~
      'test_40': event 1
        |
        |  461 |   i = *p;
        |      |   ~~^~~~
        |      |     |
        |      |     (1) use of uninitialized value '*p' here
        |

    to:

    malloc-1.c: In function 'test_40':
    malloc-1.c:461:5: warning: use of uninitialized value '*p' [CWE-457]
[-Wanalyzer-use-of-uninitialized-value]
      461 |   i = *p;
          |   ~~^~~~
      'test_40': events 1-2
        |
        |  460 |   int *p = (int*)malloc(sizeof(int*));
        |      |                  ^~~~~~~~~~~~~~~~~~~~
        |      |                  |
        |      |                  (1) region created on heap here
        |  461 |   i = *p;
        |      |   ~~~~~~
        |      |     |
        |      |     (2) use of uninitialized value '*p' here
        |

    and this helps readability of the resulting warnings, especially in
    more complicated cases.

    gcc/analyzer/ChangeLog:
            * checker-path.cc (event_kind_to_string): Handle
            EK_REGION_CREATION.
            (region_creation_event::region_creation_event): New.
            (region_creation_event::get_desc): New.
            (checker_path::add_region_creation_event): New.
            * checker-path.h (enum event_kind): Add EK_REGION_CREATION.
            (class region_creation_event): New subclass.
            (checker_path::add_region_creation_event): New decl.
            * diagnostic-manager.cc
            (diagnostic_manager::emit_saved_diagnostic): Pass NULL for new
            param to add_events_for_eedge when handling trailing eedge.
            (diagnostic_manager::build_emission_path): Create an interesting_t
            instance, allow the pending diagnostic to populate it, and pass it
            to the calls to add_events_for_eedge.
            (diagnostic_manager::add_events_for_eedge): Add "interest" param.
            Use it to add region_creation_events for on-stack regions created
            within at function entry, and when pertinent dynamically-sized
            regions are created.
            (diagnostic_manager::prune_for_sm_diagnostic): Add case for
            EK_REGION_CREATION.
            * diagnostic-manager.h (diagnostic_manager::add_events_for_eedge):
            Add "interest" param.
            * pending-diagnostic.cc: Include "selftest.h", "tristate.h",
            "analyzer/call-string.h", "analyzer/program-point.h",
            "analyzer/store.h", and "analyzer/region-model.h".
            (interesting_t::add_region_creation): New.
            (interesting_t::dump_to_pp): New.
            * pending-diagnostic.h (struct interesting_t): New.
            (pending_diagnostic::mark_interesting_stuff): New vfunc.
            * region-model.cc
            (poisoned_value_diagnostic::poisoned_value_diagnostic): Add
            (poisoned_value_diagnostic::operator==): Compare m_pkind and
            m_src_region fields.
            (poisoned_value_diagnostic::mark_interesting_stuff): New.
            (poisoned_value_diagnostic::m_src_region): New.
            (region_model::check_for_poison): Call
            get_region_for_poisoned_expr for uninit values and pass the resul
            to the diagnostic.
            (region_model::get_region_for_poisoned_expr): New.
            (region_model::deref_rvalue): Pass NULL for
            poisoned_value_diagnostic's src_region.
            * region-model.h (region_model::get_region_for_poisoned_expr): New
            decl.
            * region.h (frame_region::get_fndecl): New.

    gcc/testsuite/ChangeLog:
            * gcc.dg/analyzer/data-model-1.c: Add dg-message directives for
            expected region creation events.
            * gcc.dg/analyzer/malloc-1.c: Likewise.
            * gcc.dg/analyzer/memset-CVE-2017-18549-1.c: Likewise.
            * gcc.dg/analyzer/pr101547.c: Likewise.
            * gcc.dg/analyzer/pr101875.c: Likewise.
            * gcc.dg/analyzer/pr101962.c: Likewise.
            * gcc.dg/analyzer/pr104224.c: Likewise.
            * gcc.dg/analyzer/pr94047.c: Likewise.
            * gcc.dg/analyzer/symbolic-1.c: Likewise.
            * gcc.dg/analyzer/uninit-1.c: Likewise.
            * gcc.dg/analyzer/uninit-4.c: Likewise.
            * gcc.dg/analyzer/uninit-alloca.c: New test.
            * gcc.dg/analyzer/uninit-pr94713.c: Add dg-message directive for
            expected region creation event.
            * gcc.dg/analyzer/uninit-pr94714.c: Likewise.
            * gcc.dg/analyzer/zlib-3.c: Likewise.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

[Bug analyzer/104224] Testcases for analyzer "uninit" from fedora-devel

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

David Malcolm <dmalcolm at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
I've added further test coverage for "uninit" based on a discussion with Steve
Grubb, as r12-7157-g91b27d984ce174.

Closing this one out.

[Bug analyzer/104224] Testcases for analyzer "uninit" from fedora-devel

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by David Malcolm <dmalcolm@gcc.gnu.org>:

https://gcc.gnu.org/g:8f6369157917a4371b5d66dfe82b84aded3b8268

commit r13-6267-g8f6369157917a4371b5d66dfe82b84aded3b8268
Author: David Malcolm <dmalcolm@redhat.com>
Date:   Tue Feb 21 16:58:36 2023 -0500

    analyzer: stop exploring the path after certain diagnostics [PR108830]

    PR analyzer/108830 reports a situation in which there are lots of
    followup -Wanalyzer-null-dereference warnings after the first access of
    a NULL pointer, leading to very noisy output from -fanalyzer.

    The analyzer's logic for stopping emitting multiple warnings from a
    state machine doesn't quite work for NULL pointers: it attempts to
    transition the malloc state machine's NULL pointer to the "stop" state,
    which doesn't seem to make much sense in retrospect, and seems to get
    confused over types.

    Similarly, poisoned_value_diagnostic can be very noisy for uninit
    variables, emitting a warning for every access to an uninitialized
    variable.  In theory, region_model::check_for_poison makes some attempts
    to suppress followups, but only for the symbolic value itself; if the
    user's code keeps accessing the same region, we would get a warning on
    each one.  For example, this showed up in Doom's s_sound.c where there
    were 7 followup uninit warnings after the first uninit warning in
    "S_ChangeMusic".

    This patch adds an extra mechanism, giving pending diagnostics the
    option of stopping the analysis of an execution path if they're saved
    for emission on it, and turning this on for these warnings:
      -Wanalyzer-null-dereference
      -Wanalyzer-null-argument
      -Wanalyzer-use-after-free
      -Wanalyzer-use-of-pointer-in-stale-stack-frame
      -Wanalyzer-use-of-uninitialized-value

    Doing so should hopefully reduce the cascades of diagnostics that
    -fanalyzer can sometimes emit.

    I added a -fno-analyzer-suppress-followups for the cases where you
    really want the followup warnings (e.g. in some DejaGnu tests, and
    for microbenchmarks of UB detection, such as PR analyzer/104224).

    Integration testing shows this patch reduces the number of probable
    false positives reported by 94, and finds one more true positive:

    Comparison: 9.34% -> 10.91%
      GOOD:  66 ->  67  (+1)
       BAD: 641 -> 547 (-94)

    where the affected warnings/projects are:

      -Wanalyzer-null-dereference: 0.00% GOOD: 0 BAD: 269 -> 239 (-30)
         Unclassified: 257 -> 228 (-29)
                      apr-1.7.0:  12 ->   5  (-7)
                           doom:   1 ->   0  (-1)
                  haproxy-2.7.1:  47 ->  41  (-6)
           ImageMagick-7.1.0-57:  13 ->   9  (-4)
                     qemu-7.2.0: 165 -> 154 (-11)

          Known false: 7 -> 6 (-1)
                       xz-5.4.0:   4 ->   3  (-1)

      -Wanalyzer-use-of-uninitialized-value: 0.00% GOOD: 0 BAD: 143 -> 80 (-63)
          Known false: 47 -> 16 (-31)
                           doom: 42 -> 11 (-31)

         Unclassified: 96 -> 64 (-32)
                  coreutils-9.1: 14 -> 10  (-4)
                  haproxy-2.7.1: 29 -> 23  (-6)
                     qemu-7.2.0: 48 -> 26 (-22)

      -Wanalyzer-null-argument: 0.00% -> 2.33% GOOD: 0 -> 1 (+1) BAD: 43 -> 42
(-1)
         Unclassified: 39 -> 38 (-1)
          due to coreutils-9.1: 9 -> 8 (-1)

        True positive: 0 -> 1 (+1)
          (in haproxy-2.7.1)

    gcc/analyzer/ChangeLog:
            PR analyzer/108830
            * analyzer.opt (fanalyzer-suppress-followups): New option.
            * engine.cc (impl_region_model_context::warn): Terminate the path
            if the diagnostic's terminate_path_p vfunc returns true and
            -fanalyzer-suppress-followups is true (the default).
            (impl_sm_context::warn): Likewise, for both overloads.
            * pending-diagnostic.h (pending_diagnostic::terminate_path_p): New
            vfunc.
            * program-state.cc (program_state::on_edge): Terminate the path if
            the ctxt requests it during updating the edge.
            * region-model.cc (poisoned_value_diagnostic::terminate_path_p):
            New vfunc.
            * sm-malloc.cc (null_deref::terminate_path_p): New vfunc.
            (null_arg::terminate_path_p): New vfunc.

    gcc/ChangeLog:
            PR analyzer/108830
            * doc/invoke.texi: Document -fno-analyzer-suppress-followups.

    gcc/testsuite/ChangeLog:
            PR analyzer/108830
            * gcc.dg/analyzer/attribute-nonnull.c: Update for
            -Wanalyzer-use-of-uninitialized-value terminating analysis along
            a path.
            * gcc.dg/analyzer/call-summaries-2.c: Likewise.
            * gcc.dg/analyzer/data-model-1.c: Likewise.
            * gcc.dg/analyzer/data-model-5.c: Likewise.
            * gcc.dg/analyzer/doom-s_sound-pr108867.c: New test.
            * gcc.dg/analyzer/memset-CVE-2017-18549-1.c: Add
            -fno-analyzer-suppress-followups.
            * gcc.dg/analyzer/null-deref-pr108830.c: New test.
            * gcc.dg/analyzer/pipe-1.c: Add -fno-analyzer-suppress-followups.
            * gcc.dg/analyzer/pipe-void-return.c: Likewise.
            * gcc.dg/analyzer/pipe2-1.c: Likewise.
            * gcc.dg/analyzer/pr101547.c: Update for
            -Wanalyzer-use-of-uninitialized-value terminating analysis along
            a path.
            * gcc.dg/analyzer/pr101875.c: Likewise.
            * gcc.dg/analyzer/pr104224-split.c: New test, based on...
            * gcc.dg/analyzer/pr104224.c: Add
            -fno-analyzer-suppress-followups.
            * gcc.dg/analyzer/realloc-2.c: Add
            -fno-analyzer-suppress-followups.
            * gcc.dg/analyzer/realloc-3.c: Likewise.
            * gcc.dg/analyzer/realloc-5.c: Likewise.
            * gcc.dg/analyzer/stdarg-1-ms_abi.c: Likewise.
            * gcc.dg/analyzer/stdarg-1-sysv_abi.c: Likewise.
            * gcc.dg/analyzer/stdarg-1.c: Likewise.
            * gcc.dg/analyzer/symbolic-1.c: Likewise.
            * gcc.dg/analyzer/symbolic-7.c: Update for
            -Wanalyzer-use-of-uninitialized-value terminating analysis along a
            path.
            * gcc.dg/analyzer/uninit-4.c: Likewise.
            * gcc.dg/analyzer/uninit-8.c: New test.
            * gcc.dg/analyzer/uninit-pr94713.c: Update for
            -Wanalyzer-use-of-uninitialized-value terminating analysis along a
            path.
            * gcc.dg/analyzer/zlib-6a.c: Add -fno-analyzer-suppress-followups.

    Signed-off-by: David Malcolm <dmalcolm@redhat.com>

[Bug analyzer/104224] Testcases for analyzer "uninit" from fedora-devel

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104224

--- Comment #6 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Given the above patch, we now need -fno-analyzer-suppress-followups if you want
to see all the warnings in the testcase (rather than just stopping after the
first).